The Best Homemade Sloppy Joes

I just went to a friend's house for dinner. She made these sloppy joes and they were AMAZING. They come from www.thechunkychef.com The Best Homemade Sloppy Joes.

Ingredients:
1 Tbsp butter
1 tsp olive oil
1 lb ground beef
1/3 green bell pepper, minced
1/2 large yellow onion, minced
3 cloves garlic, minced
1 Tbsp tomato paste
2/3 cup ketchup
1/3 cup water
1 Tbsp brown sugar
1 tsp yellow mustard
3/4 tsp chili powder
1/2 tsp Worcestershire sauce
1/2 kosher salt
1/4 tsp red pepper flakes
1/4 tsp black pepper
dash of hot sauce

Instructions:
1. Heat butter and oil in a large skillet over Med/Med-High heat. Add beef and brown breaking apart into crumbles as it cooks, about 5 minutes. Transfer to a colander to drain.

2. Add onion and bell pepper to the same skillet and cook 2-3 minutes, until soft. Add garlic and cook 30 seconds or so, until fragrant. Add beef back into the skillet and add the tomato paste. Stir Well.

3. Add ketchup, water, brown sugar, mustard, chili powder, Worcestershire sauce, salt, red pepper flakes, and black pepper. Stir well to combine.

4. Cook over MED head for 10-15 minutes, unite mixture has thickened to your liking. Remove from heat and serve over toasted buns.